High deuteration of methanol in L1544

Abstract

Isotopic fractionation is a very powerful tool to follow the evolution of material from one stage to the next in the star-formation process. Pre-stellar cores exhibit some of the highest levels of deuteration because their physical conditions greatly favor deuteration processes. Deuteration maps are a measure of the effectiveness of the deuteration across the core, and they are useful to study both the deuteration as well as the formation mechanism of the main species. Methanol is the simplest O-bearing complex organic molecule (COM) detected in the interstellar medium (ISM). It represents the beginning of molecular complexity in star-forming regions, thus a complete understanding of its formation and deuteration is a necessary step to understand the development of further chemical complexity. In this paper, we use single-dish observations with the IRAM 30 m telescope and state-of-the-art chemical models to investigate the deuteration of methanol towards the prototypical pre-stellar core L1544. We also compare the results of the chemical models with previous observations of deuterated methanol towards the pre-stellar cores HMM1 and L694-2. The spectra extracted from the CHD${}_2$OH map show that the emission is concentrated in the center and towards the north-west of the core. Using deep observations towards the dust and the methanol peaks of the core, we derive a very large deuterium fraction for methanol ($\sim 20\%$) towards both peaks. The comparison of our observational results with chemical models has highlighted the importance of H-abstraction processes in the formation and deuteration of methanol. Deep observations combined with state-of-the-art chemical models are of fundamental importance in understanding the development of molecular complexity in the ISM. Our analysis also shows the importance of non-LTE effects when measuring the D/H ratios in methanol.

arXiv commentAccepted for publication in ACS Earth and Space Chemistry (Eric Herbst Festschrift)

References in corpus (57)

• Cold Dark Clouds: The Initial Conditions for Star Formation
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Probing the evolutionary status of starless cores through N2H+ and N2D+ observations
• How to Calculate Molecular Column Density
• Molecular ions in L1544. II. The ionization degree
• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• The 2014 KIDA network for interstellar chemistry
• N2H+ and C18O Depletion in a Cold Dark Cloud
• Observing the gas temperature drop in the high-density nucleus of L 1544
• The ancient heritage of water ice in the solar system
• The origin of complex organic molecules in prestellar cores
• Formation of Complex Molecules in Prestellar Cores: a Multilayer Approach
• The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core
• H-atom addition and abstraction reactions in mixed CO, H2CO and CH3OH ices: an extended view on complex organic molecule formation
• Chemistry in Disks. IV. Benchmarking gas-grain chemical models with surface reactions
• A cold complex chemistry toward the low-mass protostar B1-b: evidence for complex molecule production in ices
• CO Depletion and Deuterium Fractionation in Prestellar Cores
• Dynamics and Depletion in Thermally Supercritical Starless Cores
• Testing grain surface chemistry : a survey of deuterated formaldehyde and methanol in low-mass Class 0 protostars
• The Degree of CO Depletion in Pre-stellar Cores
• Depletion and low gas temperature in the L183 prestellar core : the N2H+ - N2D+ tool
• Structure and kinematics of the Taurus star-forming region from Gaia-DR2 and VLBI astrometry
• Astrochemical evolution along star formation: Overview of the IRAM Large Program ASAI
• The Different Structures of the Two Classes of Starless Cores
• Gas phase Elemental abundances in Molecular cloudS (GEMS) I. The prototypical dark cloud TMC 1
• Deuterated methanol in the pre-stellar core L1544
• The dynamics of collapsing cores and star formation
• Gas-grain chemistry in cold interstellar cloud cores with a microscopic Monte Carlo approach to surface chemistry
• Chemical differentiation in a prestellar core traces non-uniform illumination
• Complex organic molecules in low-mass protostars on solar system scales -- I. Oxygen-bearing species
• Benchmarking spin-state chemistry in starless core models
• The observed chemical structure of L1544
• The Central 1000 au of a Pre-stellar Core Revealed with ALMA. II. Almost Complete Freeze-out
• Production of complex organic molecules: H-atom addition versus UV irradiation
• High sensitivity maps of molecular ions in L1544: I. Deuteration of N2H+ and HCO+ and first evidence of N2D+ depletion
• The central 1000 AU of a pre-stellar core revealed with ALMA. I. 1.3 mm continuum observations
• Interstellar detection of c-C3D2
• Mapping deuterated methanol toward L1544: I. Deuterium fraction and comparison with modeling
• High D/H ratios in water and alkanes in comet 67P/Churyumov-Gerasimenko measured with the Rosetta/ROSINA DFMS
• The ALMA-PILS survey: The first detection of doubly-deuterated methyl formate (CHD2OCHO) in the ISM
• Prestellar grain-surface origins of deuterated methanol in comet 67P/Churyumov-Gerasimenko
• Diffusion activation energy and desorption activation energy for astrochemically relevant species on water ice show no clear relation
• The complex organic molecular content in the L1498 starless core
• Interferometric observations of warm deuterated methanol in the inner regions of low-mass protostars
• Detection of Complex Organic Molecules in Young Starless Core L1521E
• Modeling deuterium chemistry in starless cores: full scrambling versus proton hop
• Seeds of Life in Space (SOLIS). III. Zooming into the methanol peak of the pre-stellar core L1544
• Successive deuteration in low-mass star-forming regions: the case of D${}_2$-methanol (CHD${}_2$OH) in IRAS 16293-2422
• Methanol deuteration in high-mass protostars
• Modelling Deuterated Isotopologues of Methanol toward the Pre-Stellar Core L1544
• H2CS deuteration maps towards the pre-stellar core L1544
• Multi-line observations of CH${}_3$OH, c-C${}_3$H${}_2$ and HNCO towards L1544: Dissecting the core structure with chemical differentiation
• Modelling methanol and hydride formation in the JWST Ice Age era
• Deuteration of c-C${}_3$H${}_2$ towards the pre-stellar core L1544
• First detection of CHD${}_2$OH towards pre-stellar cores
• Cosmic-ray ionisation rate in low-mass cores: the role of the environment

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• Broadband infrared spectroscopy of methanol isotopologues in pure, H2O-rich, and CO-rich ice analogues